Effect of Left Atrial Decompression by Percutaneous Balloon Mitral Commissurotomy on the Atrial Electrophysiologic Properties

ABSTRACT

BACKGROUND AND OBJECTIVES: Atrial dilatation contributes to the inducibility of atrial fibrillation (AF) by changing the atrial electrophysiological properties. There has been no report regarding the electrophysiologic data of the left atrium (LA), where the most significant electrophysiological impact might be expected to occur in case of mitral stenosis (MS). We investigated the electrophysiological changes after reduction of the LA pressure in patients who were undergoing percutaneous balloon mitral commissurotomy (PBMC). SUBJECTS AND METHODS: We studied 26 patients (21 women, age range 50+/-12 years) with MS, including 7 sinus rhythm (SR) patients. The effective refractory period (ERP), the monophasic action potential duration (MAPD90), and the conduction time (CT) were measured simultaneously in both atriums at 600, 500, 400 and 300 ms of drive cycle length (DCL). The restitution slope (RS) was also calculated by the S1S2 method. The atrial fibrillation cycle length (AFCL) and dominant frequency (DF) for the cases of AF were also calculated. All the measurements were repeated after PBMC. RESULTS: The mean LA pressure was significantly reduced after PBMC in both the AF and SR patients (17.0+/-5.5 mmHg vs 10.4+/-4.0 mmHg, respectively, p<0.01, 17.6+/-7.1 mmHg vs 9.0+/-2.8 mmHg, respectively, p<0.01). A significant increase of ERP was observed in the LA after PBMC, but not in the right atrium (RA). The increase of MAPD90 after PBMC was significant in the LA at all the tested DCLs, but not in the RA. The CT was also significantly decreased at all the tested DCLs after PBMC. The RS of the LA decreased from 1.71+/-0.82 to 0.76+/-0.33 after PBMC (p=0.056). However, no significant changes of the AFCL or DF after PBMC were observed in the AF group. CONCLUSION: Chronic atrial stretch altered the atrial electrophysiological milieu, especially in the LA, which was partially reversible in SR patients. This result supports the theoretical basis for the beneficial effects of early intervention to reduce the atrial pressure overload in MS patients.